The present invention relates to a data communicating system for controlling plural air conditioning machines.
In a prior communicating system, in which plural air conditioning machines installed in factories and/or offices are controlled by a remote controller, an interface is provided corresponding to each air conditioning machine. An output terminal of a primary interface is connected to input terminals of secondary interfaces by a common cable. The primary interface is connected to a primary remote controller. One or more of the secondary interfaces are connected to one or more secondary remote controllers, respectively.
In addition, in the prior art, the primary remote controller communicates on a routine periodic basis with the primary interface. The primary interface determines if a command from the primary remote controller for the run mode of the air conditioning machines has changed. When the command has changed, the primary interface communicates the changed command to the secondary interfaces corresponding to the other air conditioning machines, and the run mode of the air conditioning machines is changed.
Moreover, the primary interface also routinely communicates with the secondary interfaces. A signal, which indicates the presence or absence of a malfunction in an air conditioning machine, is transmitted to the primary interface from the corresponding secondary interface. A display on each primary and secondary remote controller shows the run mode of each air conditioning machine and the presence or absence of a malfunction.
If all of the air conditioning machines are in a shutdown mode and it is then desired to start them, all of the air conditioning machines cannot be started simultaneously to avoid an excessive starting current. Therefore, in the prior art, in order to prevent an excessive starting current, the primary interface transmits starting command signals to the secondary interfaces and indicating signals (to cause the displays of all the primary remote controller and secondary remote controllers to indicate the changed status) in a staggered manner separated by a fixed time interval, for example, 4 seconds.
Problems in the prior art construction are as follows.
Firstly, since the starting command signal and the indicating signal are outputted together, when the air conditioning machines are started from the shutdown mode, the display of the secondary remote controller, corresponding to a last air conditioning machine which is started, does not show the run mode until after all the air conditioning machines are started.
Therefore, a certain period of time is required until all the displays show the run mode.
Secondly, since routine communications continuously pass between the primary interface and each of the secondary interfaces, the probability of a communication malfunction becomes greater.